1. Technical Field
The invention relates to an apparatus for driving a solid-state imaging device mounted on a digital camera or the like, and more particularly to a solid-state imaging device driving apparatus and a digital camera that can generate various driving pulses with using small memory resources, to drive the solid-state imaging device.
2. Description of Related Art
A CCD- or CMOS-type solid-state imaging device which is used a digital still camera, a digital video camera, a camera-equipped mobile phone, or the like (hereinafter, such an apparatus is referred to as a digital camera) is driven by driving pulses generated by an imaging device driving apparatus. In a CCD-type solid-state imaging device, for example, a vertical charge transfer path (VCCD) is driven by a vertical transfer pulse, and a horizontal charge transfer path (HCCD) is driven by a horizontal transfer pulse.
Such driving pulses are generated on the basis of data of a pulse changing point, those of a repetition number (loop number), and the like which are previously stored in a register and a memory. Many kinds of timing pulses are used for driving the solid-state imaging device. Moreover, the waveforms of the pulses are complicated depending on the difference of driving modes (for example, the normal transfer mode and the high-speed transfer mode). As a result, there arises a problem in that the amount of data used in generating the driving pulses is large, and a register and a memory for storing such data must have a large capacity.
Therefore, JP 2002-51270 A discloses such a configuration that four memories are provided. The first memory holds time series data (logical status), the second memory holds a value of a length of time period between a pulse changing point and the next changing point, the third memory holds a repetition number of logical changes during one period and the fourth memory holds a repetition number of the periods themselves. The data stored in the four memories are combined to generate various driving pulses.
Recently, user's request for a digital camera increases. In a digital camera, in order to increase functions and enhance its performance, driving pulses for a solid-state imaging device are complicated in period and pulse waveform, and the amount of data required for generating the driving pulses goes on increasing. JP 2002-51270 A can deal cope with two-mode and two-stage loop driving pulses. When further multi modes and further multi loop stages of driving pulses are required, the memory capacity must be increased.
Also, each time when the design specification of a digital camera is changed to increase functions, data for generating driving pulses are inevitably changed. When the pulse generation is not highly flexible, cost for designing pulse data would be increased.